Numerical Simulation Study on Casing Strength of Underground Gas Storage and an Optimization Method of Casing

摘要

The casing of underground gas storage is under complex stress conditions because of the injection-production alternating loads and the influence coming from the intensive injection and withdrawal of injection-production wells. It is crucial for the long-term safety of injection-production wells of underground gas storage to conduct casing optimization and to decrease casing stress. A three-dimensional parametric finite element model of injection-production well of underground gas storage was built by employing the finite element software ABAQUS and the PYTHON scripting language. The whole process of model building was recorded by the PYTHON scripting language. It is very easy to automatically build a different model by editing and running the PYTHON script file. The model includes casing, cement sheath and formation. The spiral perforation completion was conducted in the model. The injection-production process was simulated by adopting the data coming from a field injection-production well of underground gas storage. The temporal and spatial distribution of von Mises stresses of the model was obtained from the simulation results. In order to check if the casing stress can meet relevant safety requirements, the von Mises stress of the casing was checked by employing the fourth stress strength criterion. A study on the influence of the model parameters was carried out by changing the parameters one by one, as a result of which the optimal structure and dimensions of the casing were obtained.